package com.nic.view.widget;

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Created by Administrator on 2018/9/3.
 */

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {


    private int spanCount;//多少列
    private int spacing;//间距
    private boolean includeEdge;//是否有边缘

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {

        this.spanCount = spanCount;

        this.spacing = spacing;

        this.includeEdge = includeEdge;

    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {


        int position = parent.getChildAdapterPosition(view); // item position

        int column = position % spanCount; // item column

        if (includeEdge) {

            outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)

            outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) { // top edge

                outRect.top = spacing;

            }

            outRect.bottom = spacing; // item bottom

        } else {

            outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)

            outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)

            if (position >= spanCount) {
                outRect.top = spacing; // item top

            }
        }
    }
}

